Which sentence best summarizes the article? A
Scientists are trying to make sure that no endangered species becomes completely extinct.

B
Scientists believe that 25 percent of all mammals and 10 percent of all bird species will be extinct within three decades.

C
Scientists want to preserve the DNA of endangered species in a frozen state, so they can later make clones of the animals.

D
The DNA, which determines an animal's characteristics, will be preserved at a very low temperature.